Optimising decommissioning of oil and gas pipelines with respect to the commercial fishing sector on the UK continental shelf.

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The oil and gas (O&G) and commercial-fishing sectors are among the two largest stakeholders that use the UK continental shelf (UKCS), particularly the North Sea. Evidence suggests that fishermen currently target pipelines, a poorly understood activity which has multi-sector implications for decommissioning. The challenge, as identified by the partners, is: the regulator and their advisers need to understand commercial fishing practices around pipelines in order to predict the consequences of various pipeline decommissioning options to both the O&G and fishing sectors. Such an understanding will enable the identification of the most cost-effective, legislatively compliant, safe and environmentally sustainable pipeline decommissioning option. This approach will reduce costs to all stakeholders and, ultimately, the UK taxpayer. To enable exploitation of UK Continental Shelf (UKCS) oil and gas (O&G), more than 45,000 km of pipelines have been installed since the 1960s [1]. Only 2% have been decommissioned and there has been little research on the consequences of decommissioning to other industries and the environment. Many of the pipelines are reaching the end of their useful lives and need decommissioning. Unlike platforms, pipelines are not covered by the OSPAR 98/3 ban on the disposal of installations at sea [2]. Pipeline decommissioning is considered on a case-by-case basis, by comparative assessment of the options. Operators must show that any proposed strategy meets international obligations to ensure the safety of navigation and fishing, and protection of the marine environment [1]. In the UKCS, fishing is an ecologically and economically important activity[3]. Due to the overlap of the O&G and fishing industries there is inevitably physical interaction between the two, including damage to fishing gear from pipelines [4] and to pipelines from fishing gear [5]. Vessels are banned from fishing within the 500 m exclusion zone around platforms [6], but no such restrictions apply to pipelines. Anecdotal accounts of vessels targeting pipelines as fishing grounds have always existed, with vessels thought to potentially benefit by targeting fish attracted to pipelines [7,8]. In 2014, analyses jointly undertaken by SAMS and MSS quantified the extent of this interaction and found that over a third of North Sea (NS) demersal trips fish occurred within 200 m of a pipe. The choice of decommissioning strategy of the ~2500 oil and gas pipelines will therefore have implications for the fishing industry and the environment.The proposed project brings together the regulator (Department of Environment and Climate Change), their advisers (Marine Scotland Science) and representatives of the fishing and O&G sectors (Scottish Fishermen's Federation and Oil and Gas UK respectively) to extend the 2014 analysis(see above) and translate it into predictions of the impact of a range of realistic decommissioning scenarios (e.g. 0 - 100 % pipeline removal, covering pipelines with rocks, pipeline-size dependent removal etc) on the fishing industry. The first stage will be to collate data on pipeline attributes (size, protective material, date of installation) and fishing behaviour around pipelines and identify 'hotspots' of pipeline/fishing interactions by quantifying and characterising the location where pipelines are frequently crossed as fishermen move between grounds. The impact of realistic decommissioning options will then be determined. The final stage of the project is to embed this new knowledge into the relevant stakeholder community (e.g. regulators, their advisers and industry). This will be achieved via knowledge-brokering events (e.g. multi-sector workshops), via industry-publications and, directly, via the project partners themselves.